Exposure to cigarette smoke in the womb may interfere with the brain‘s reward system, and make children more vulnerable to addictions.

According to the Centers for Disease Control, 13% of women say they smoked during the last three months of their pregnancy, despite studies that have correlated lighting up with an increased risk of birth defects and heart trouble for their children. Now, a new study published in the journal JAMA Psychiatry adds to that list of risks, showing that exposure to smoke in utero may interfere with proper development of the baby’s reward processing system in the brain.

Researchers from Technische Universität Dresden in Germany compared 177 teens between the ages 13 to 15 who had been exposed to cigarettes prenatally to 177 teens whose mothers did not smoke while expecting. To test how the teens reacted to being presented with a reward — which simulated the need to satisfy an addiction — the participants were placed in a functional MRI (fMRI) scan to record their brain activity while they performed specific computer-based tasks. The teens were asked to press a button indicating on which side of the screen a figure popped up, and they were told there would be a reward if they were able to press the correct button fast enough. The scientists also varied the time that the targets appeared on the screen in order to evaluate how quickly the teens processed the anticipated task. Based on previous work with animals that suggested that activity in a specific area of the brain, the ventral striatum, was depressed by nicotine, the researchers focused their attention on this region of the adolescents’ brains.

Indeed, they saw less activity in this area of the brain among the teens whose were exposed to smoke in the womb compared to those who were not, which resulted in longer times to respond to the target. Similar inhibited responses may be behind some addictions, since muted activity of the brain chemicals that signal satisfaction may prompt people to continue to seek this “high” and become dependent on addictive substances or behaviors. “The weaker responsivity of the ventral striatum to regard anticipation in prenatally exposed adolescents may represent a risk factor for substance use and development of addiction later in life. This result highlights the need for education and preventive measures to reduce smoking during pregnancy,” the study authors wrote.

Children with attention deficit-hyperactivity disorder (ADHD) also show inhibited activity in the ventral striatum, and other studies linked lower activity in this region among teens to more risky behaviors, such as reckless driving, that extend beyond taking illegal drugs. Adolescence is already a time when the brain is undergoing dramatic changes in learning about risk and reward, and the latest results highlight how early exposure to chemicals such as nicotine could further interfere with that development.

The results certainly don’t suggest that cigarette smoking during pregnancy always causes addictions or substance abuse problems in children later, but they do add to the growing body of data documenting the harms that nicotine can have on proper fetal development. With some women still smoking while pregnant, they hope that these data will fuel more education efforts that inform mothers-to-be about the dangers of smoking for the unborn.